Fuel atomising nozzles



United States Patent 30 l Dowty Fuel Systems Limited, Cheltenham,England I Application October 11, 1956, Serial No. 615,290

Claims priority, application Great Britain October 11, 1955 7 Claims.(Cl. 299114) This invention relates to liquid spray nozzles of the spilltype particularly for use with liquid fuel burners. The invention isconcerned with the spill type of nozzle which comprises a swirl chamberinto which liquid enters tangentially under high pressure, a circulardischarge orifice co-axial with the swirl chamber at one end thereof,and a circular spill orifice co-axial with the swirl chamber at theopposite end thereof, this spill orifice having a diameter not less thanthat of the discharge orifice. spill flow may be controlled, forexample, by a restriction to flow in the spill line leading from thespill orifice. The advantage of a spill spray nozzle is that adequateatomization of the sprayed liquid takes place over a large range ofspray fiow rates, since the energy in the vortex is independent of therate of discharge. Much thought has gone into the designing of spillspray nozzles to obtain the maximum efficiency and one feature of suchdesign is the provision of a diffusing chamber behind the spill orificewhere swirling motion of the spilled liquid is reduced and its kineticenergy converted into liquid pressure thus avoiding an unnecessarilylarge pressure drop between supply and spill lines.

My research into spill spray nozzle design leads me to think thathowever well the spill orifice and diffusing chamber are designed andmade there is inevitably considerable loss of swirl energy in thespilled liquid. This is due to the fact that the liquid swirls at highspeed over the spill orifice and difiusing chamber surfaces so thatfriction and viscosity absorb a considerable amount of swirl energy.Thus the conversion of swirl energy into liquid pressure cannot be veryefiicient. In particular this eficiency will be very low Where theliquid is of a viscous nature.

The manufacture of a spill spray nozzle requires high accuracy and highsurface finish of the spray orifice, spill orifice, swirl chamber, anddifiusing chamber where efiiciency in operation and matching of aplurality of nozzles is required. By the term matching reference is madeto the arrangement of a set of nozzles directly connected to commonsupply and spill lines which will all operate at substantially similarflow rates without the employment of fiow equalising devices.

Such an arrangement is highly desirable for an aircraft gas turbinewhere a plurality of spray nozzles must be used.

Spill spray nozzles of the kind referred to operate with a central aircore in the swirling liquid, this air core extending from the sprayorifice through the swirl chamber into the spill orifice. For use withaircraft gas turbines it is highly desirable that air from this air coreshould not enter the spill line and for this purpose the spill orificeof each nozzle should include a base or bafile to prevent external airentering the spill line.

The main object of the present invention is to provide an efiicientconstruction of spill spray nozzle of the type referred to which is of asimple nature, the number of accurately formed and highly finishedcomponents being reduced to a minimum by the substantial elimination ofthe diifusing chamber.

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A further object is to provide a spill spray nozzle construction of thekind referred to by which a plurality of the nozzles may be useddirectly connected to common supply and return lines, all of the nozzlesoperating at substantially the same individual flow rates without theuse of special fiow equalizers. A still further object is to provide aspill spray nozzle construction or" the kind referred to in which thedanger of air entering the spill line is eliminated.

In accordance with the present invention in a spill spray nozzle of thetype referred to, the spill orifice opens rearwardly into a diametrallyextending passage having a. forwardly facing rear wall of which thecentral portion constitutes the base or bafiie for the air core of theswirling liquid, the said passage having outlet openings in its twoouter ends which lead to a common spill line. Preferably these outer endportions of the base wall are inclined in the sense of fiow away fromthe central portion. By these means the provision of a diffusing chamberhaving an accurate highly finished surface is eliminated, theoperation'being that liquid passing in a swirling manner through thespill orifice is suddenly prevented from swirling as it enters thepassage, conversion of the swirl energy into pressure thus beingaccomplished by a ram effect. Whilst this conversion cannot be said tobe the most theoretically efficient it does not involve diffusingchamber losses and in fact a spill spray nozzle in accordance with thisinvention is found to operate at about the same 'eificiency as a moreusual spill spray nozzle employing a diffusing chamber. The making ofthe diametral passage, when this is done by slotting transversely theend of a male member interfitted with a female member, is a more simplemanufacturing operation than the making of a highly finished diffusingchamber since the passage itself need not be highly finishedor ofaccurate dimensions. This is due to the fact that once the high velocityswirl is eliminated the flow of liquid is reduced and frictional lossesare accordingly less.

The nozzle preferably comprises a plurality of elements clampedco-axially in end-to-end relation, one element including the base of theswirl chamber and the spill orifice whilst the adjoining elementincludes the passage conveniently formed as a slot which is locatedagainst the outer end of the element including the spill orifice.

A preferred embodiment of the invention for use as a spill spray nozzlein a combustion chamber of an aircraft gas turbine will now be describedwith reference to the accompanying drawings, in which:

Figure 1 is a side elevation of the nozzle with one half in section andFigure 2 is a perspective view of one element of the burner.

The nozzle shown comprises an annular inlet passage 11 surrounding aco-axial spill passage 12. The inlet passage 11 conducts liquid fuel toa pair of tangential inlet orifices 15 formed in the cylindrical wall 13of a swirl chamber 14. Forwardly the swirl chamber 14 terminates in acoaxial spray orifice 16 and rearwardly it terminates in a co-axialspill orifice 17. The spill orifice is of greater diameter than thespray orifice and is formed in an element 18 which is spigo-ted into theelement constituting the swirl chamber. Thar:- is spigoted into theelement 18 a further element 19 which apart from a diametral slot 20closes the space within the element 18 at the rear of the spill orifice17. The diametral slot 20 has a forwardly facing rear Wall comprisingthree fiat portions namely a central portion 21 and inclined endportions 22. The element 19 is hollow and each end portion 22 has anoutlet opening 23 formed therein leading into the hollow of the elementwhich forms the beginning of the common spill line or passage 3 12. Thecentral portion 21 forms the base or bafiie for the air core in theswirling fuel and positively prevents air from this air core passinginto the spill line 12. The width of the slot 20 is preferablysubstantially equal to the diameter of the spill orifice 17 and theoutlet-openings 23 are large enough not to present any undue restrictionto flow into the spill line 12. The amount of fuel that is caused todischarge asa conical spray from the spray orifice 16 depends on controlmeans outside the burner whereby the desired resistance to flow alongthe spill line is created. However, this control means is outside thescope of the present invention. The various elements which go to make upthe nozzle are clamped together by means of an internal flange 24 at theforward end of an external shroud 25 by means of an internal nut 26. Anexternal flange 27 at the base of the shroud 25 forms the means by whichthe whole burner is clamped to a supporting pipe 28 by means of theclamping ring 29. The pipe 28 in fact encloses the fuel supply passage11 and liquid from this passage through holes 30 in the internal nut 26to the space between the various burner elements and the inside of theshroud 25. Thus V 4 orifice, for exit of the liquid from said passage tothe spill line after traversing said passage.

2. A spill spray nozzle as claimed in claim I, wherein V the said nozzlebody includes one element having formed with the first element.

the supply fuel obtains access to the tangential openings the swirlchamber 14. V 6

The dimensions of the-slot formed at the end of the element 1 are notcritical, but it should be of the same width as the spill orifice 17 orslightly wider. A

high surface finish to this orifice is not necessary since swirlingmotion of fuel from the spill orifice is stopped when it enters the slotand the velocityof fuel along the slot is thus comparatively slow sothat frictional losses with the slot walls are not important. Thus theneed for the provision of an accurately formed highly finished diffusingchamber is eliminated and is substituted simply by the formation of theslot 20 which is not critical as regards dimensions or surfaceifinish.

The embodiment described is of course only anjexarnple of the inventionand various modifications may be made i particularly. with regard todiametral passage. 1

I claim as my invention: a l. A spill spray nozzle for connection tosupply' and the formation 015- the spill lines, respectively, saidnozzle comprising a nozzle body chambered to define a circular-sectionedswirl chamber tangentially ported for communication. with the supplyline and having-at one end a central spray orifice and at its oppositeend a central spill orificeof larger diameter, said body being formedbeyond the spill orifice from the spray orifice with two generallyparallel side walls disposed in planes parallel to and at opposite sidesof the axis of the body, a bottom Wall directed transversely of thataxis, and a top wall generally parallel therein the base of the swirlchamber and the spill orifice, and a second elementclamped to the firstelement in endwise co-axial arrangement having therein a diametral slotwhich forms the diametral passage in conjunction 3. A spill spray burneras claimed in claim 2, wherein the said second element .has an internalbore which is in connectionwith thespill lineand with the ends of thediametra'l slot.

4. A spill spray burner as claimed in claim 3, wherein the width of thediametral' slot'is not less than the diameter of the spill orifice.

5. A spill spray burnerasclaimed in claim 4, wherein the base of theslot includes a plaincentralportion facing towards the spill orifice. a

6. A spill spray nozzieas clainied in claim 5 wherein 7. A-spill spraynozzle'for connection tosupply'and spill lines, respectively said nozzlecomprisingahollow shroud andannular coaxial elementstherein cooperatingtherewith and ported to define a circular-sectioned-and axially disposedswirl ehamber a surroundingysupply chamber, tangentially directedsupply'ports admitting liquid from the supply chamber to the swirlchamber,

an axially disposed spillline, a central spray orifice hat the outer-endof the swirl chamber; and a central spill orifice of largerdiameteratthe inner;endof the swirl chamber, one ofsaid-elementsadjoining another along matching transverse surfaceslocated at--the inner end of t the spill orifice, one of said twoelements being slotted V diametrally in its --matching surface, todefinetwo generally transverse side walls 'disposed parallel to and atopposite sides of the bodys axis, and a bottom Wall joining the two sideWalls and .disposed generally transverse to such axis, the slot being ofa Width generally corresponding to the diameter of the spill orifice,and extending at its end portions beyond such diameter, these endportions being closedin by the matching member to definediametralpassages, of which a surface'of the A matching memberconstitutes a top wall, and outlet ports formed in the inner of said twoelements, adjacent the,

outer ends of said passages, and communicating with the spill line.

to the bottom wall but pierced centrally by the spill Y orifice, saidside, bottom and top walls defining a transverse passage openingcentrally to and receiving liquid from the spillorifice, and extendingradially outwardly thereof, and outlet ports formed in said body,opening at the ends of said passage radially outwardly of the spillReferences Cited in the file of patent UNITED STATES PATENTS

